Pioneer VSX108 I have a constant hum in the speakers attached to my Pioneer VSX108 reagrdless of what the source or settings are.

Here ya go...

Power and Accessory Wiring:

Red = 12v Switched Source (Ignition)
Yellow = 12v Constant Source (Battery)
Black = Ground (Chassis)
Orange = Illumination (Dashboard Lights)
Blue with White = Power Antenna Up / Down Signal
Blue = Amplifier Power On / Off Signal


Speaker Wiring:

White / White & Black = Left Front speaker + / -
Green /Green & Black = Left Rear speaker + / -
Gray / Gray & Black = Right Front speaker + / -
Violet / Violet & Black = Right Rear speaker + / -

Is the hum in the receiver-attached speakers or the sub?

Self-powered sub?

How is the sub attached - RCA or speaker-level?

Disconnect the input(s) and see if it hums in the absence of an audio source. A bad audio cable shield or unwisely-routed audio cables will allow entrance of unwanted signals from external power sources, magnetic fields, even dimmer-controlled track lights. Sometimes, simply reversing the orientation of the ac power plug can eliminate humming.

If it hums with the sub attached, unplug the sub's power cord. Differences in AC ground potentials will generate hum across linked devices.

It sounds like you might have a grounding issue. Try connecting to the wall outlet with a ground prong lifting adapter. Not just the speakers but the source plugged into the speakers also. Good luck.

Neither the amp or the sub have grounded power cords.

I have discovered the ML Dynamo takes about 30 minutes to switch to standby in auto mode.

With speaker level inputs connected to the Onkyo A807 amp, both units powered from the same wall outlet, Dynamo sub on Auto, the sub hums for about half an hour after the Onkyo is switched off, then the sub goes quiet. Not so good.

I connected a bonding wire between the two units on 3_7_09. If I smoked some old audio gear I could just look at that as an opportunity, right?

Works fine. Now I have the ML powered from the wall and working normally.

The hum you hear from the speakers and from the unit itself originate with 60hz AC power. They may not actually be related. Sometimes a transformer will hum slightly and unnoticeably. That you're getting a loud speaker hum says there is an electrical leak or a grounding issue somewhere.

Do all sources produce the hum or, say, just the phono? How about on headphones? Try rotating the AC plug. In those days they weren't keyed with one large blade as they are now.

You're probably picking up 60hz AC hum. Through WHAT program sources? You need to isolate the source(s) before an answer can be given. Just phono or any other single source? Bad connection of the RCA cables or bad grounding. Try flipping the AC cord polarity around on the affected component.

Hums come from several sources. A light dimmer switch on the wall. Speakers too close to a monitor or other electrical device. Try turning off everything in the room or nearby rooms, one at a time while the hum is audible.

Power source harmonics. Or its power supply regulation. Check also if input line is touching something.

Turn down the second amplifier (which the speakers are connected to). This hum is the amplified 'noise' from the EQ and/or amplifier. Try using a much higher graded second amp (eq 500w)

The constant power (yellow wire) needs to be connected to an unswitched +12V source. It sounds like that's either unconnected or you've connected it to a switched power source.